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OBJECTIVE To evaluate the effects of 2 fractions of inspired oxygen (Fio 2 s) during anesthesia on postanesthesia Pao 2 and other measures of oxygen exchange. ANIMALS 22 healthy adult sexually intact female dogs undergoing ovariohysterectomy by ventral midline celiotomy. PROCEDURES Dogs were randomly assigned to receive either oxygen (Fio 2 > 0.9 [100% oxygen]; n = 11; control group) or a mixture of nitrogen and oxygen (Fio 2 = 0.4; 11; 40% oxygen group) as the carrier gas for isoflurane while anesthetized. All dogs were allowed to breathe spontaneously while anesthetized. For each dog, the Pao 2 , Paco 2 , other indices of oxygenation, and extent of sedation were monitored at predetermined times during and for 1 hour after anesthesia. Measured variables were compared between the 2 treatment groups and over time within each treatment group. RESULTS None of the measured variables differed significantly between the control and 40% oxygen groups at any time during the postanesthesia period. Within each treatment group, the Paco 2 and extent of sedation decreased over time during the postanesthesia period. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that indices of oxygenation did not differ significantly between healthy dogs in which the Fio 2 was maintained at > 0.9 and those in which the Fio 2 was maintained at 0.4 while anesthetized for ovariohysterectomy. Thus, the addition of nitrogen to the carrier gas for an inhalant anesthetic conferred neither an advantage nor disadvantage in regard to oxygenation during the first hour of anesthesia recovery.

A positive staircase effect is well documented during neuromuscular monitoring. However, the increase in twitch amplitude may not remain stable over time. We compared the staircase phenomenon and twitch stability during single twitch (ST) or train-of-four (TOF) stimulation in anesthetized dogs. Force of contraction was measured in ten dogs. Each thoracic limb was stimulated with ST 0.1 Hz or TOF q 12 s for 25 min (random order). No neuromuscular blockers were administered. Every 5 min, ST and T1 amplitudes were compared within and between groups. Stability of twitch amplitude (<5 % change in 5 min) was also evaluated. ST and T1 amplitude increased over time without significant differences between groups. After 10 min of ST stimulation, the average ST amplitude had increased significantly to 107 %, and remained unchanged thereafter. T1 amplitude was significantly greater than baseline only at 5 (111 %) and 10 min (109 %); a decline towards baseline occurred thereafter. Stability was reached after 15 min for all dogs in the ST group, however, three dogs continued to have changes >5 % with TOF. An initial increase in ST amplitude remained stable over the observation period, but the increase in T1 amplitude during TOF was frequently followed by a decay. A stable twitch amplitude (variation <5 % in 5 min) was observed in all dogs with ST after 15 min of stimulation, which was not the case during TOF stimulation. Therefore, it appears at least in dogs, that ST might offer some advantages over T1 for measuring twitch amplitude.

Abstract Objective To assess the ability to visually detect fade during train-of-four (TOF) or double burst stimulation (DBS) in anesthetized dogs recovering from nondepolarizing neuromuscular block. Study design Online anonymous survey. Population Data from 112 participants. Methods A web-based survey containing 12 videos of the response to ulnar nerve stimulation with TOF and 12 with DBS obtained at different levels of recovery from rocuronium-induced block was distributed to participants of the American College of Veterinary Anesthesia and Analgesia and the Academy of Veterinary Technicians in Anesthesia and Analgesia e-mail lists. Participants were asked to provide their highest training degree in anesthesiology, watch each video no more than twice, and determine whether fade was present. The probability to correctly recognize fade was calculated using binomial general linear models. General linear models and Tukey's tests were used to assess the effects of level of neuromuscular block, pattern of stimulation, and observers' training on the probability to detect fade. Results The survey was completed by 53 diplomates, 29 licensed veterinary technicians, 24 residents and six doctors of veterinary medicine (DVMs). The probability to detect fade decreased as partial neuromuscular block became more shallow (p < 0.0001). A TOF or DBS ratio of 0.7 had a 50% chance of being detected. DBS was superior to TOF for detecting fade when the ratio was 0.3–0.69. TOF was superior to DBS when the ratio was 0.7–0.9 (p < 0.0001). There were no differences among groups of observers when assessing fade with TOF or DBS. Conclusions and clinical relevance Detection of fade from observations of the response to TOF in dogs is unreliable. Advance training in anesthesiology or the use of DBS confers little to no advantage for this subjective test. [ABSTRACT FROM AUTHOR]